Sunny skies over wide areas from northern Japan to the Kansai region are expected on Sunday.

As temperatures are expected to rise, weather officials are issuing warnings of heatstroke dangers.

Daytime highs may reach 39 degrees Celsius in Kumagaya City in Saitama Prefecture, and 38 degrees in the cities of Fukushima and Maebashi in Gunma Prefecture.

The urban areas of Yamagata, Utsunomiya, Kofu, Fukui and Kyoto are expected to see the temperatures rise to 37 degrees Celsius.

Most residents of the main island of Honshu, as well as Shikoku, are also being warned of heatstroke dangers.

They are advised to stay indoors during daytime hours if possible, drink plenty of water, use air-conditioning and remove facemasks when appropriate.

Moist air flowing in from the south is likely to bring heavy rain to some areas in southern Kyushu and Shikoku through noon on Sunday.

As temperatures rise, atmospheric conditions are likely to grow unstable in Kanto-Koshin and Tohoku, causing torrential rain with local thunderclaps.

The Meteorological Agency is calling on people to be on alert for landslides, flooding in low-lying areas and swollen rivers, as well as lightning strikes and gusty winds, including tornadoes.